Is the Catholic Mass really the same all around the world every time it is celebrated?

Yes! No matter where or when you go to Mass, you will always know what you’re going to get. 
 
Jesus Christ celebrated the first Mass with His disciples at the Last Supper, the night before He died. He commanded His disciples, “Do this in remembrance of me” (Luke 22:19). The celebration of the Mass then became the main form of worship in the early Church, as a reenactment of the Last Supper, as Christ had commanded. 
 
Each and every Mass since commemorates Jesus’ sacrifice on the cross through the Holy Eucharist. Because the Mass “re-presents” (makes present) the sacrifice on Calvary, Catholics all around the world join together to be made present in Christ’s timeless sacrifice for our sins. There is something fascinating about continuing to celebrate the same Mass—instituted by Christ and practiced by the early Church—with the whole community of Catholics around the world…and in heaven.